Meta-analysis of total and differential white blood cell counts in schizophrenia

Objective: Schizophrenia is associated with alterations in blood inflammatory markers, including cytokines. Total white blood cell (WBC) count is a marker of low-grade inflammation. We conducted a meta-analysis of total and differential WBC counts in patients with schizophrenia. Method: Articles were identified through a systematic search of PsycINFO, Pub Med, Web of Science, and the associated references. Data were analyzed using a random effects approach. Results: Twenty-four studies met the inclusion criteria. Blood total WBC, monocytes, and neutrophils were significantly higher in schizophrenia vs. controls with small-to-medium effect sizes (standardized mean difference [SMD] = 0.39–0.53, P < 0.01 for each). In first-episode psychosis compared with controls, neutrophils and monocytes were significantly increased with similar effect sizes (SMD = 0.40–0.41, P ≤ 0.01 for each), and there was a trend for higher total WBC (SMD = 0.46, P = 0.05). Conclusions: Consistent with studies of other inflammatory markers, we found evidence for increased total and differential WBC counts in schizophrenia. Our results complement other studies of WBC counts in schizophrenia. These findings are relevant to the pathophysiology and potentially the treatment of schizophrenia.